The GLN1 gene, encoding glutamine synthetase in Saccharomyces cerevisiae, was sequenced, and its encoded polypeptide was shown to have significant homology to other eukaryotic glutamine synthetases. S1 analysis has defined the transcriptional start site of the gene. Upstream analysis of the gene using lacZ fusions has verified transcriptional control of the gene and has identified a nitrogen upstream activation sequence which is required for the increased transcription of GLN1 seen when glutamine is replaced by glutamate as the nitrogen source. cis-acting sites required for the increased transcription in response to purine starvation also have been localized.